Digital rights management (DRM) systems are well-known in the art. A description of one example of such a system is found on the World Wide Web at:
www.openmobilealliance.com/docs/DRM%20Short%20Paper%20DEC%202003%20.pdf
In a typical DRM environment, a content server provides content to a DRM server. The DRM server is typically also provided, from the content server or from another appropriate source, with access rules indicating which entities are to be enabled to access the content, and with what rights; typical examples of rights include the following non-limiting list: no access; render only; render only a certain number of times; free preview, copy once; and copy many.
The DRM server typically outputs scrambled or encrypted content (termed herein “scrambled content”), scrambled or encrypted in accordance with any appropriate scrambling or encryption scheme, such as, for example, AES or triple-DES. The terms “scrambled” and “encrypted”, in all their grammatical forms, are used interchangeably throughout the present specification to refer to any appropriate form of scrambling or encrypting, as is well-known in the art.
The DRM server typically outputs a key for descrambling or decrypting the content. As is well-known in the art, such a key may be supplied “as is” or in, for example, any of the following forms: encrypted with one or more group keys, as is well-known in the art; as an entitlement control message (ECM) for input to a one-way function at a receiver of the ECM in order to produce the key; as an encrypted ECM for decryption at a receiver of the ECM (such as a mobile device), it being appreciated that the ECM form is particularly useful in broadcast systems such as the well-known DVB-H; as an encrypted key within a rights object.
Typical methods useful in handling such keys are described, for example, in the following patents and published patent applications, the disclosures of which are hereby incorporated herein by reference: U.S. Pat. Nos. 5,282,249 and 5,481,609 to Cohen et al; and GB Published Patent Application 2353682 of NDS Limited and corresponding U.S. patent application Ser. No. 09/502,867 of Itkis.
Additionally, the DRM server typically outputs one or more tamper resistant or tamper proof rights objects, each rights object including appropriate information implementing one or more of the access rules as described above, for interpretation by a DRM agent associated with the receiver of the content.
In typical digital rights management systems, content is sent to a content receiver and stored in secured form. When content is to be accessed (for example, rendered), a secure application interprets one or more rights objects associated with the device or user who has requested a particular type of access (rendering in the present example). If rendering by the requestor is permitted, the secure application determines the content key (using an appropriate method based on the manner in which the content key is encrypted or otherwise protected, as described above) and provides the content as requested (in the present example, renders the content).
Digital rights management systems useful in connection with mobile telephony typically face certain challenges because of the nature of the mobile telephone handset environment, the mobile telephone handset being the receiver in the case of a mobile telephony system.
In typical presently commercially available DRM systems, because content is stored in scrambled form, applications which are to access the content must be customized in order to provide the functions described above. One example of a commercially available DRM system for mobile telephone is the Mobile DRM System, available from NDS Limited, One London Road, Staines, Middlesex TW18 4EX, United Kingdom.
A standard for mobile DRM systems is presently being developed by the Open Mobile Alliance; information about the Open Mobile Alliance is available via the Internet on the World Wide Web, at www.openmobilealliance.org. It is believed that, in some of the current implementations, in Open Mobile Alliance systems, and in other systems, content is descrambled and stored “in the clear” in a temporary area so that it can be played by a standard application.
The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.